Androgen biosynthesis in the stomach: expression of cytochrome P450 17 alpha-hydroxylase/17,20-lyase messenger ribonucleic acid and protein, and metabolism of pregnenolone and progesterone by parietal cells of the rat gastric mucosa

Cortisol, DHEA, and Sexual Steroid Concentrations in Fattening Pigs' Hair

Simple Summary

The rearing of heavy pigs in Italy is an important part of the production of Protected Designation of Origin (PDO) hams. Along with the standard quality characteristics, the quality of products with animal origin is also assessed by the level of animal welfare. Evaluation of hair steroid concentrations has been considered an effective approach to assess stress in mammals. The advantage of using hair for this process is that it provides an integrated measure of hormone concentrations over medium- and long-term periods, it can be simply and non-invasively collected, and it does not require any special expedient for storage. The aim of this study was to evaluate the hair cortisol, dehydroepiandrosterone (DHEA), and sexual steroid concentrations in fattening pigs at 36 weeks of age before slaughtering through a non-invasive approach. Females had significantly higher cortisol levels, significantly lower concentrations of DHEA, and significantly higher cortisol/DHEA ratios than barrows. Progesterone was significantly higher in gilts than in barrows. Testosterone and 17β-estradiol were significantly higher in barrows than in gilts. These results will allow us to plan future research with the aim of identifying threshold values in order to set up strategies to control the allostatic load and to increase the resilience of fattening pigs.

Abstract

The aim of this study was to analyze the feasibility and reliability of using hair as a matrix to determine the dehydroepiandrosterone (DHEA) and sexual steroid concentrations and the cortisol/DHEA ratio in fattening pigs. The results could be also used to plan future research to identify threshold values in order to set up strategies to control the allostatic load and increase the resilience of fattening pigs before slaughter. The study was conducted on 107 commercial crossbred rearing pigs. The hair samples were taken by shaving at the age of 36 weeks, and concentrations of the hormones were measured using a solid-phase microtiter radioimmunoassay. Females had significantly higher cortisol levels (p < 0.01), significantly lower DHEA concentrations (p < 0.05) and significantly higher cortisol/DHEA ratios (p < 0.01) than barrows. Progesterone was significantly higher in gilts than in barrows (p < 0.01). Testosterone and 17β-estradiol were significantly higher in barrows than in gilts (p < 0.05). If future research can produce threshold values for the different markers examined, the evaluation of animals under subclinical stress conditions will be possible.

The acid-secreting parietal cell as an endocrine source of Sonic Hedgehog during gastric repair

Sonic Hedgehog (Shh) has been shown to regulate wound healing in various tissues. Despite its known function in tissue regeneration, the role of Shh secreted from the gastric epithelium during tissue repair in the stomach remains unknown. Here we tested the hypothesis that Shh secreted from the acid-secreting parietal cell is a fundamental circulating factor that drives gastric repair. A mouse model expressing a parietal cell-specific deletion of Shh (PC-ShhKO) was generated using animals bearing loxP sites flanking exon 2 of the Shh gene (Shh(flx/flx)) and mice expressing a Cre transgene under the control of the H(+),K(+)-ATPase β-subunit promoter. Shh(flx/flx), the H(+),K(+)-ATPase β-subunit promoter, and C57BL/6 mice served as controls. Ulcers were induced via acetic acid injury. At 1, 2, 3, 4, 5, and 7 days after the ulcer induction, gastric tissue and blood samples were collected. Parabiosis experiments were used to establish the effect of circulating Shh on ulcer repair. Control mice exhibited an increased expression of Shh in the gastric tissue and plasma that correlated with the repair of injury within 7 days after surgery. PC-ShhKO mice showed a loss of ulcer repair and reduced Shh tissue and plasma concentrations. In a parabiosis experiment whereby a control mouse was paired with a PC-ShhKO littermate and both animals subjected to gastric injury, a significant increase in the circulating Shh was measured in both parabionts. Elevated circulating Shh concentrations correlated with the repair of gastric ulcers in the PC-ShhKO parabionts. Therefore, the acid-secreting parietal cell within the stomach acts as an endocrine source of Shh during repair.

The molecular biology, biochemistry, and physiology of human steroidogenesis and its disorders

Steroidogenesis entails processes by which cholesterol is converted to biologically active steroid hormones. Whereas most endocrine texts discuss adrenal, ovarian, testicular, placental, and other steroidogenic processes in a gland-specific fashion, steroidogenesis is better understood as a single process that is repeated in each gland with cell-type-specific variations on a single theme. Thus, understanding steroidogenesis is rooted in an understanding of the biochemistry of the various steroidogenic enzymes and cofactors and the genes that encode them. The first and rate-limiting step in steroidogenesis is the conversion of cholesterol to pregnenolone by a single enzyme, P450scc (CYP11A1), but this enzymatically complex step is subject to multiple regulatory mechanisms, yielding finely tuned quantitative regulation. Qualitative regulation determining the type of steroid to be produced is mediated by many enzymes and cofactors. Steroidogenic enzymes fall into two groups: cytochrome P450 enzymes and hydroxysteroid dehydrogenases. A cytochrome P450 may be either type 1 (in mitochondria) or type 2 (in endoplasmic reticulum), and a hydroxysteroid dehydrogenase may belong to either the aldo-keto reductase or short-chain dehydrogenase/reductase families. The activities of these enzymes are modulated by posttranslational modifications and by cofactors, especially electron-donating redox partners. The elucidation of the precise roles of these various enzymes and cofactors has been greatly facilitated by identifying the genetic bases of rare disorders of steroidogenesis. Some enzymes not principally involved in steroidogenesis may also catalyze extraglandular steroidogenesis, modulating the phenotype expected to result from some mutations. Understanding steroidogenesis is of fundamental importance to understanding disorders of sexual differentiation, reproduction, fertility, hypertension, obesity, and physiological homeostasis.

Oxidative Stress-Mediated Brain Dehydroepiandrosterone (DHEA) Formation in Alzheimer's Disease Diagnosis

Neurosteroids are steroids made by brain cells independently of peripheral steroidogenic sources. The biosynthesis of most neurosteroids is mediated by proteins and enzymes similar to those identified in the steroidogenic pathway of adrenal and gonadal cells. Dehydroepiandrosterone (DHEA) is a major neurosteroid identified in the brain. Over the years we have reported that, unlike other neurosteroids, DHEA biosynthesis in rat, bovine, and human brain is mediated by an oxidative stress-mediated mechanism, independent of the cytochrome P450 17α-hydroxylase/17,20-lyase (CYP17A1) enzyme activity found in the periphery. This alternative pathway is induced by pro-oxidant agents, such as Fe(2+) and β-amyloid peptide. Neurosteroids are involved in many aspects of brain function, and as such, are involved in various neuropathologies, including Alzheimer's disease (AD). AD is a progressive, yet irreversible neurodegenerative disease for which there are limited means for ante-mortem diagnosis. Using brain tissue specimens from control and AD patients, we provided evidence that DHEA is formed in the AD brain by the oxidative stress-mediated metabolism of an unidentified precursor, thus depleting levels of the precursor in the blood stream. We tested for the presence of this DHEA precursor in human serum using a Fe(2+)-based reaction and determined the amounts of DHEA formed. Fe(2+) treatment of the serum resulted in a dramatic increase in DHEA levels in control patients, whereas only a moderate or no increase was observed in AD patients. The DHEA variation after oxidation correlated with the patients' cognitive and mental status. In this review, we present the cumulative evidence for oxidative stress as a natural regulator of DHEA formation and the use of this concept to develop a blood-based diagnostic tool for neurodegenerative diseases linked to oxidative stress, such as AD.

Complex assembly on the human CYP17 promoter

Optimal steroid hormone biosynthesis occurs via the integration of multiple regulatory processes, one of which entails a coordinate increase in the transcription of all genes required for steroidogenesis. In the human adrenal cortex adrenocorticotropin (ACTH) activates a signaling cascade that promotes the dynamic assembly of protein complexes on the promoters of steroidogenic genes. For CYP17, multiple transcription factors, including steroidogenic factor-1 (SF-1), GATA-6, and sterol regulatory binding protein 1 (SREBP1), are recruited to the promoter during activated transcription. The ability of these factors to increase CYP17 mRNA expression requires the formation of higher order coregulatory complexes, many of which contain enzymatic activities that post-translationally modify both the transcription factors and histones. We discuss the mechanisms by which transcription factors and coregulatory proteins regulate CYP17 transcription and summarize the role of kinases, phosphatases, acetyltransferases, and histone deacetylases in controlling CYP17 mRNA expression.

Molecular Specificity of 5-Androstenediol as a Systemic Radioprotectant in Mice

We compared in vivo radioprotective efficacy of 5-androstenediol (5-AED) to that of ten other steroids: 17alpha-androstenediol, dehydroepiandrosterone, 5-androstenetriol (AET), 4-androstenedione (AND), testosterone, estradiol, fluasterone, 16alpha-bromoepiandrosterone, 16alpha-fluoro-androst-5-en-17alpha-ol (alpha-fluorohydrin, AFH), and 16alpha-fluoro-androst-5-en-17beta-ol (beta-fluorohydrin). Steroids were administered 24 or 48 hr before, or 1 hr after, whole-body gamma-irradiation. Two days after irradiation at 3 Gy, blood elements were counted. In addition, after irradiation at 9-12.5 Gy, survival was recorded for 30 days. The results showed radioprotective efficacy was specific for 5-AED. One other steroid, AFH, demonstrated appreciable survival effects but was less efficacious than 5-AED. AND and AET produced slight enhancement of survival in some experiments. This is the first demonstration that the prophylactic window for survival enhancement by 1 subcutaneous (s.c.) injection of 5-AED is as long as 48 hr in mice. Moreover, the results indicate that 1 s.c. injection of 5-AED 1 hr after irradiation is much less effective than 1 injection 24-48 hr before irradiation. Comparing the molecular features of steroids with radioprotective efficacy leads to the following conclusions: 1) these effects are due to interaction with specific receptors, since s.c. injection of extremely similar molecules with the same physicochemical properties as 5-AED were not radioprotective; 2) the 17-hydroxyl group is essential; 3) this group must be in the beta configuration in the absence of nearby side groups; 4) a halogen atom at 16 changes the 17-hydroxyl specificity to alpha; 5) the 3beta-hydroxyl group is not essential; 6) addition of a 7beta-hydroxyl group is deleterious; and 7) the effects are not due to activation of sex steroid receptors.

Estrogen and progesterone receptor isoforms expression in the stomach of Mongolian gerbils

AIM: We studied the estrogen receptor (ER) and progesterone receptor (PR) isoforms expression in gastric antrum and corpus of female gerbils and their regulation by estradiol (E2) and progesterone (P4).

METHODS: Ovariectomized adult female gerbils were subcutaneously treated with E2, and E2 + P4. Uteri and stomachs were removed, the latter were cut along the greater curvature, and antrum and corpus were excised. Proteins were immunoblotted using antibodies that recognize ER-alpha, ER-beta, and PR-A and PR-B receptor isoforms. Tissues from rats treated in the same way were used as controls.

RESULTS: Specific bands were detected for ER-alpha (68 KDa), and PR isoforms (85 and 120 KDa for PR-A and PR-B isoforms, respectively) in uteri, gastric antrum and corpus. We could not detect ER-beta isoform. PR isoforms were not regulated by E2 or P4 in uterus and gastric tissues of gerbils. ER-alpha isoform content was significantly down-regulated by E2 in the corpus, but not affected by hormones in uterus and gastric antrum.

CONCLUSION: The presence of ER-alpha and PR isoforms in gerbils stomach suggests that E2 and P4 actions in this organ are in part mediated by their nuclear receptors.

Possible Association of Heart Failure Status With Synthetic Balance Between Aldosterone and Dehydroepiandrosterone in Human Heart

Background— Aldosterone is produced not only in the adrenal gland but also in the extra-adrenal tissues, including failing human heart. This study examined the production of dehydroepiandrosterone (DHEA) in human heart and elucidated the possible physiological significance.

Method and Results— Using left ventricular tissues obtained at autopsy, reverse transcription–polymerase chain reaction followed by Southern blot analysis revealed the gene expressions of CYP17. By measuring plasma aldosterone and DHEA levels at the coronary sinuses and aortic roots during cardiac catheterization, we found that DHEA but not aldosterone was secreted from control subjects ( P <0.0001 and P =0.74, respectively), whereas aldosterone but not DHEA was secreted from patients with heart failure ( P =0.0017 and P =0.67, respectively). To examine the significance of DHEA, we measured myocyte cell sizes and the gene expression of B-type natriuretic peptide (BNP), using a neonatal rat cardiocyte culture system. We found that DHEA (10 −8 mol/L) significantly inhibited the increase in myocyte cell sizes and BNP mRNA levels upregulated by endothelin-1 ( P =0.031 and P <0.0001, respectively).

Conclusions— CYP17 gene expression and production of DHEA were demonstrated in human control heart. Also, we found that cardiac production of DHEA was suppressed in failing heart. We postulated that DHEA and/or its metabolites exert a cardioprotective action through antihypertrophic effects.

Gastric acid secretion of normal Japanese subjects in relation to Helicobacter pylori infection, aging, and gender

BACKGROUND

In Japan, where the incidence of gastric cancer is high, Helicobacter pylori infection could affect gastric acid secretion differently from that in Western countries. The aim of this study was to investigate the relationship between H. pylori infection, acid secretion, aging, and gender in normal Japanese subjects.

METHODS

The study comprised 193 Japanese subjects who had undergone routine endoscopy. Gastrin-stimulated acid output was performed during the routine endoscopic examination using the endoscopic method of gastric acid secretory testing (EGT: endoscopic gastrin test), which has been reported previously. H. pylori status was determined by histology, rapid urease test, and serology.

RESULTS

Mean EGT values were 3.9 +/- 1.5 mEq/10 min in H. pylori-negative men, 1.6 +/- 2.5 in H. pylori-positive men, 2.2 +/- 0.9 in H. pylori-negative women, and 1.5 +/- 1.2 in H. pylori-positive women. Although acid secretion was lower in H. pylori-positive subjects compared with H. pylori-negative subjects in both men and women, the decrease was more marked in men with H. pylori infection. Multiple linear regression analysis showed that aging is positively associated with gastric acid secretion in the H. pylori-negative subjects, whereas a negative association was found between them in the H. pylori-positive subjects.

CONCLUSIONS

In Japanese subjects, aging affects gastric acid secretion differently depending on the status of H. pylori infection. H. pylori infection showed a stronger inhibitory effect on the acid secretion in men than in women. This gender-related difference in the susceptibility of acid secretion to H. pylori infection may explain the higher rates of gastric cancer in men in Japan.

Gastric parietal cells: potent endocrine role in secreting estrogen as a possible regulator of gastro-hepatic axis

Estrogen, if it is produced in the gastrointestinal tract, may overflow into the systemic circulation in the case of increased portal-systemic shunting. This idea is in accord with a significant step-up in serum estradiol (E2) concentration in the portal vein of rats, compared with that in the artery. Gene expression of aromatase, estrogen synthetase, was demonstrated by RT-PCR in the gastric mucosa of male and female adult rats, equivalent to that in the ovary. Aromatase activity and production of E2 in the gastric mucosa were demonstrated by (3)H(2)O assay and gas chromatography-mass spectrometry, and they were inhibited by aromatase inhibitor, 4-hydroxyandrostenedione. Conversion of (14)C-androstenedione to (14)C-E2 through (14)C-testosterone in cultured gastric mucosa was also demonstrated. Parietal cells exhibited strong signals for aromatase mRNA and immunoreactive protein by in situ hybridization histochemistry and immunohistochemistry. Estrogen receptor alpha mRNA and immunoreactive protein were demonstrated in hepatocytes by RT-PCR, in situ hybridization histochemistry, and immunohistochemistry. Total gastrectomy reduced portal venous E2 concentration, without changing systemic E2 concentration, together with down-regulation of estrogen receptor alpha mRNA level in the liver. These findings indicate that gastric parietal cells play a potent endocrine role in secreting estrogen that may function as a regulator of the gastro-hepatic axis.

Regulation of HSD17B1 and SRD5A1 in lymphocytes

We previously reported lymphocyte expression of genes encoding enzymes required for steroid metabolism; however, only 17beta-HSD and 5alpha-reductase showed significant enzyme activity. We now investigate regulation of lymphocyte expression for genes encoding 17beta-HSD and 5alpha-reductase. Cultured human T and B lymphoid cell lines and peripheral blood mononuclear cells were treated with known regulators of steroidogenic gene expression including forskolin, PMA, ionomycin, various steroids, interleukin (IL)-4, and IL-6. Treatment with 10 or 50 microM forskolin resulted in a 20-60% reduction of expression for HSD17B1 (encoding 17beta-HSD I) in T and B lymphoid cell lines and peripheral blood mononuclear cells, although such a change was not observed in the expression of SRD5A1 (encoding 5alpha-reductase I). No significant changes were found when cells were treated for 24 h with various concentrations of PMA or ionomycin. Incubation with 10(-9) to 10(-7) M androstenedione or estradiol increased expression of HSD17B1, while testosterone decreased the expression of this gene. SRD5A1 expression was increased in the presence of 5alpha-DHT although no consistent changes were observed when the cells were treated with testosterone. Other steroids, including dexamethasone, progesterone, and 6-hydroxypregnanolone, produced no effects on expression of either HSD17B1 or SRD5A1. Treatment with 0.1-10 ng/ml of IL-4 or IL-6 also did not effect significant changes in gene expression. These data implicate the involvement of the cAMP-protein kinase signal transduction pathway in regulating lymphocyte expression of HSD17B1. Furthermore, it appears that lymphocyte HSD17B1 and SRD5A1 are regulated to some extent by specific steroids.

Development and differentiation of the interstitial and tubular compartments of fetal porcine testes

Male differentiation is initiated by fetal testicular androgen synthesis, catalyzed by the enzyme 17alpha-hydroxylase/17,20 lyase cytochrome P450 (P450c17). This study was an investigation of testicular development and differentiation in porcine fetuses recovered on Days 30-42 of gestation. The expression of P450c17 was localized in fetal gonads by in situ hybridization and immunocytochemistry and related to cellular proliferation through expression of the proliferating cell nuclear antigen (PCNA). Gonadal P450c17 expression was quantified by Western immunoblot analysis and related to testosterone secretion by cultured explants of fetal gonads. P450c17 transcripts were detected in the interstitium surrounding testicular cords preceding the appearance of the enzyme protein. The intensity of both P450c17 hybridization and staining was greater in Yorkshire fetal gonads, which also exhibited more advanced tubular development. PCNA staining was prominent within tubular primordia and was higher in testes from Yorkshire than from Meishan fetuses on all days examined. P450c17 expression paralleled testosterone secretion, which decreased by Day 42, and was generally less in cultures of Meishan than of Yorkshire fetal gonads. These data demonstrate that the expression of P450c17 in porcine fetal testes coincides with differentiation of central medullary cells and androgen secretion during gonadal development between Days 30 and 42 of gestation. This occurs as medullary cords organize and is associated with changes in cellular proliferation within the tubular compartment.

Androgen synthesis in a songbird: a study of cyp17 (17alpha-hydroxylase/C17,20-lyase) activity in the zebra finch

Androgens and estrogens influence the maturation and function of numerous tissues in both male and female birds, especially the brains of the oscine songbirds. Although there exist a very large number of studies that have investigated circulating sex steroids in many species of wild and captive-held songbirds, there remain a significant number of questions about the sites of synthesis of the active steroids that act on the songbird brain. Estrogens are derived from androgen. Thus, the synthesis of androgen itself is critical for both androgen- and estrogen-dependent actions in both male and female songbirds. Therefore, we have undertaken studies of the enzyme 17alpha-hydroxylase/C17,20-lyase (Cyp17), the enzyme responsible for the synthesis of androgens from their progestin or pregnane precursors via their 17alpha-hydroxy intermediates. Here we have characterized optimal conditions for measuring Cyp17 in gonads of adult zebra finches via the conversion of tritiated [3H]progesterone into 17alpha-hydroxy P (17alpha-hydroxylase activity) and androstenedione and testosterone (C17,20-lyase) activity. Cyp17 activity is abundant in testis, with lesser amounts in ovary. Low levels of Cyp17 activity were also detected in male adrenals, but not in any other tissue, including brain. Testicular Cyp17 activity is readily inhibited in vitro by ketoconazole, a specific Cyp17 inhibitor. Ketoconazole works less well in vivo. In males castrated and/or treated with fadrozole, an inhibitor of aromatase, we detected no extragonadal sites of Cyp17 activity, although fadrozole appeared to increase circulating androgens in both castrated and intact males. Thus, we still do not know the site of androgen synthesis in these males. Further studies of Cyp17 will be useful in understanding more about the mechanisms of androgen delivery to neural circuits in adult and developing songbirds.

Prominent sex steroid metabolism in human lymphocytes

Steroid metabolism was investigated in cultured human B-lymphoblastoid cells (B-LCL), and peripheral blood T and B cells. Gene expression was examined by reverse-transcription polymerase chain reaction amplification (RT-PCR). Appropriate sized transcripts were detected in both cultured and fresh peripheral lymphocytes for CYP11A, CYP17, HSD11L (11beta-hydroxysteroid dehydrogenase I), HSD17B1 (17beta-hydroxysteroid dehydrogenase type I) and SRD5A1 (5alpha-reductase I). B-LCL, but not T and B cells, expressed CYP11B. There was minimal expression of HSD3B1 and HSD3B2 (3beta-hydroxysteroid dehydrogenase I and II) in B-LCL and T cells. Transcripts for CYP19 and HSD11K were not detected. Corresponding enzymatic activity was detectable only for 17-hydroxysteroid dehydrogenase and 5alpha-reductase, respectively producing testosterone and 5alpha-dihydrotestosterone. Steroid identities were confirmed by gas chromatography/mass spectrometry (GC/MS). One metabolite thought to be deoxycorticosterone was identified by GC/MS as 6alpha-hydroxypregnanolone. It was concluded that sex hormone metabolism, including androgen synthesis, occurs in lymphocytes, and may modulate immune response.

Twenty-four-hour basal and repetitive pentagastrin-stimulated gastric acid secretion in normal and sham-operated rats and in rats after gonadectomy or treatment with estradiol or testosterone

BACKGROUND

Studies in different species have suggested, but not established, that sex hormones influence gastric acid secretion. We studied how acid output is affected by the sex hormones estradiol or testosterone in vivo and in vitro.

METHODS

In gastric fistula rats that were normal, sham-operated, neonatally gonadectomized, or treated with estradiol or testosterone, 24-h basal and pentagastrin-stimulated acid secretion was measured. The in vitro effects of estradiol and testosterone on histamine-induced aminopyrine accumulation in isolated parietal cells were also determined.

RESULTS

Basal acid output was similar in the two sexes, but stimulated secretion was significantly higher (34%; P < 0.01) in males. Ovariectomy did not influence acid output, whereas orchidectomy reduced basal (18%; NS) and stimulated 24-h secretion (P < 0.01). Estradiol decreased (23%; NS) the 24-h basal output in females but not in males. Estradiol suppressed stimulated secretion in females (29%, P < 0.01) and males (42%, P < 0.01) during the day. At night the stimulated secretion increased in both females (17%, NS) and males (32%, P < 0.05). A similar pattern was found when rats were treated with testosterone. In vitro, estradiol and testosterone reduced histamine-stimulated aminopyrine accumulation in both female and male isolated parietal cells.

CONCLUSIONS

Estradiol and testosterone both appear to influence gastric secretion in rats, and their action differs between day and night, between the sexes, and between basal and stimulated secretion.